Process for solubilizing lubricating oil additives



R C-O-Zn-O-C I R ii A Patented Aug. .18,

I UNITED STATE.

4 2,293,419 S-PATENT OFFICE 1 rnocnss FOR sowmuzmo ILUBBICATING OIL ADDITIVES Paul B. Van Ess, Berkeley CaliL, assignor to Shell Development Company, San Francisco, Calif.,

a corporation of Delaware No Drawing. Application May 27, '1941,

Serial No. 395,391

6 Claims.

' tendency to become stuck in the grooves; lacquer and/or carbon formation appear to be the principal reasons for this occurrence.

The addition of small amounts of certain metal salts of alkylated aromatic hydroxy monocarboxylic acids in which the carboxylic acid radical is attached directly to the ring, preferably in ortho position to the OH radical, when added to mineral oils is known to be especially effective in reducing ring-sticking tendencies of mineral oils. The aromatic jhydroxy carboxylic acids may be monoor poly-nuclear, suitable acids being, for

example, alkyl salicylic, ortho hydroxy naphthoic or anthracene ortho hydroxy carboxylic acids.

Suitable alkyl radicals are particularly those hav-'- ing three or more carbon atoms, such as n or isopropyl, butyl, amyl, cetyl wax, etc. radicals. One or several monocarboxylicalkyl radicals may be attached to the nucleus. ,Of the,polyvalent metals which may be used to form the salts, mag-- nesium, calcium, strontium, barium, zinc, tin, nickel, manganese, lead, copper, cobalt and aluminum are the most useful. I

Many of the substances which are unusually useful as anti-ringsticking agents are'dlflicult to dissolve in lubricating oils in effective quantities. To get such difllcultly soluble compounds in solution, it has been necessary to heat mixtures 01' lubricating oils and their salts to temperatures of the order of 200 C. for a prolonged time, which often causes some deterioration of the oil. I have found that when dissolving these metallic salts at the elevated temperatures necessary for dissolution a portion of the salts decompose. The decomposition is believed to proceed according to the following equations, which postulate that the normal (or basic salt, as the casemay be) is converted to an inner ring" salt.

' heat uo n salt Inner ring" salt In general, at temperatures between about .160-190 0., this reaction appears to be quite slow. Above about 190 (2., however, it may become quite rapid.

It appears that the inner ring salts formed by this conversion are far more readily soluble in hyd ocarbon oils than the "open salts, and that dissolution of difiicultly soluble salts by heating them to elevated temperatures is due to this ring closure. However, the conversion of all of the open to theinner ring salts is undesirable, because the latter have much poorer anti-ringsticking properties thanthe former. Reduclngthe temperature of this solution of the salts does not prevent the ring closure, in that the longer time required for dissolution at lower temperatures results in the formation of the ring products as well.

Now, I have discovered that the presence of r relatively small amounts of the inner ring salt in a mineral oil greatly enhances the solubility of the more desirable open salts in this oil. Thus, by carefully controlling the time and temperature of the heating, it is possible to satisfactorily dissolve the desired open salt in a mineral oil without converting an excessive amount to the ring compound. However, in practice it is difllcult to obtain the desired degree of partial conversion to Q the inner ring salt, since apparently the rate of conversion varies greatly depending on various factors, not all of which are known. For example, it is known that the salts or diflerent metals are cyclized at widely difierent rates. Thus, when heating two 1% solutions of calcium and zinc di-isopropyl salicylates, respectively, in

lubricating oil for 23 hours at 170 C., it was found that the percentages converted were 100% and respectively.

The salts which most readily form the inner ring structures are those alkylated aromatic hydroxy monocarboxylic acid salts in which the carboxylic acid radical is in ortho position to the OH radical. Therefore, I prefer them for use as solubility agents for the dissolution of other alkyl ated aromatic ortho hydroxy mono carboxylates, or of alkylated aromatic meta or para hydroxy mono carboxylates, -In order to facilitate control and to obtain stable solution of one of the diflicultly soluble salts with the minimum amount of conversion to the ring compound, I prefer to proceed as follows:

A solution of inner ring salt is first prepared by heating a mixture of a relatively small amount of the open salt andoil to between about 190- '200 0., substantially until C0: evolution has ceased. The resulting solution is then cooled to below 190 0.; and preferably between'about boxylic radical is attached directly to the aromatic nucleus under conditions toform an inner I ring salt and thereafter dissolving a quantity of 25% of which was converted to the ring com--- pound. This solution was a suitable concentrate which could be blended with straight lubricating oil in any desired proportion to produce an antiringstici-ring lubricating oil containing, say, from .5 %-2.5% of the active open salt.

In general, it is desirable to convert at least about and not more than 30%, and preferably from to of the open to the inner ring compound. The percentage converted can be determined when measuring the amount of CO2 evolved, or better yet, by determining the amounts. of free alkyl phenol in the oil before and after the heating period.

If desired, one may first dissolve and convert to the ring compound a salt of one metal and thereafter dissolve a salt of another metal. This may have certain advantages in minimizing corrosiveness of the resulting finished oil.

If an amount of the salt in excess of that which is soluble at normal room temperatures is dissolved at the elevated temperature, it may be desirable to filter the oil after cooling in order to remove the excess.

It will be obvious to those skilled in the art that other additives, such as other antl-ringsticking agents. extreme pressure compounds, antiwear agents, anti-oxidants, etc.,- can be added to the compounds prepared in accordance with my invention.

'I claim as my invention:

1. In the process of dissolving in a mineral oil a difiioultly soluble open salt combining a polyvalent metal with an aromatic hydroxy mono carboxylic acid, in which the carboxylic radical is directly connected to the aromatic nucleus to produce an anti-ringsticking lubricating oil, the improvement comprising heating a mineral oil containing a small amount of a salt formed by combining a polyvalent metal with an aromatic hydroxy mono carboxylic acid in which the caropen salt in said mineraloil to produce a lubricant with anti-ringsticking properties. g

2. In the process of dissolving in a mineral lubricating oil a difiicultly soluble open salt combining a polyvalent metal with an aromatic ortho hydroxy mono carboxylic acid in which the carboxylic radical is directly attached to the aromatic nucleus to produce an anti-ringsticking lubricating oil, the improvement comprising heating a mixture of said oil and said salt to a temperature between -200 C. under conditions to convert a minor portion only of said open salt to the corresponding inner ring salt and thereafter adding further quantities of the open salt under conditions to preclude the formation of CO2.

' 3. In the process of dissolving in a mineral oil a difficultly soluble open salt combining a polyvalent metal with an aromatic hydroxy mono carboxylic acid, in which the carboxylic radical is directly connected to the aromatic nucleus to produce an anti-ringsticking lubricating oil, the improvement comprising aiding the dissolution of said'open salt by the addition of a concentrate prepared by heating a mineral oil containing a salt combining a polyvalent metal with an aromatic hydroxy mono carboxylic acid under conditions of time and temperature to liberate CO2 and form an inner ring salt.

4. In the process of dissolving an open salt of calcium di-isopropyl salicylate in a mineral oil to produce an anti-ringsticking lubricant, the improvement comprising adding an inner ring salt of a polyvalent metal and ah aromatic hydroxyl carboxylic' acid as a solubilizing agent.

5. The process of claim 4 in which the added inner ring salt is the inner ring salt of calcium di-isopropyl salicylate.

6. The process of claim 4 in which the added inner ring salt is the inner ring salt of zinc diisopropyl salicylate.

Y PAUL R. VAN ESS. 

